A method and system for recovering lithium from a lithium-containing solution

Abstract

This invention discloses a method and system for recovering lithium from a lithium-containing solution, belonging to the field of lithium-ion battery material technology. The method for recovering lithium from a lithium-containing solution provided by this invention includes extracting the lithium-containing solution with an organic phase to obtain a supported organic phase, and then back-extracting the supported organic phase with a back-extracting agent to obtain a back-extraction system; the organic phase includes HBL121 and a diluent; the back-extracting agent contains dissolved carbon dioxide. The method provided by this invention significantly improves the extraction and back-extraction efficiency, enhances the overall lithium recovery efficiency, and increases the purity of the obtained lithium salt. It also reduces the compositional complexity of the entire extraction system, improving safety and economic efficiency. This invention also provides a system for implementing the above method, as well as applications of the above method.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a method and system for recovering lithium from a lithium-containing solution. Background Technology

[0002] Lithium is a crucial rare element for promoting modernization and the development of related industries such as science and technology. It is one of the most promising new energy sources and strategic resources, widely used in high-energy lithium batteries, rubber industry, aerospace, ceramics, lasers, medicine, welding, explosives, cement, metallurgy, and new energy fields, earning it the title of "the energy metal of the 21st century." Especially in the new energy sector, the energy released by one gram of lithium through thermonuclear reactions is equivalent to the energy produced by burning more than 20,000 tons of high-quality coal. Lithium-ion batteries and nuclear fusion power generation are currently hot research areas. Given its unique properties in the nuclear energy industry, it is also known as a "high-energy metal." Therefore, the acquisition and storage of lithium resources are extremely important.

[0003] Lithium can typically be extracted from natural resources or recovered from lithium-containing waste. Both methods usually require dissolving lithium in water and then separating it from the water, such as lithium extraction from seawater or from spent lithium-ion batteries. Methods for recovering lithium from lithium-containing solutions mainly include precipitation (e.g., lithium carbonate and lithium phosphate), dialysis, electrochemical methods, adsorption, and solvent extraction. However, precipitation consumes a lot of solvent, and the lithium content in the mother liquor remains high; dialysis consumes dialysis membranes; electrochemical methods require electricity and are currently inefficient; and in adsorption methods, the adsorbent becomes powdery, has poor flowability and permeability after repeated use. Therefore, solvent extraction is currently the most widely used method for lithium extraction.

[0004] However, solvent extraction still has problems such as low extraction efficiency, low lithium recovery rate and high cost. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for recovering lithium from lithium-containing solutions, which can effectively improve the lithium recovery rate from lithium-containing solutions and reduce the corrosion of equipment during the extraction process.

[0006] The present invention also provides a system for implementing the above-described method.

[0007] According to an embodiment of a first aspect of the present invention, a method for recovering lithium from a lithium-containing solution is provided, the method comprising extracting the lithium-containing solution with an organic phase to obtain a loaded organic phase, and back-extracting the loaded organic phase with a back-extracting agent to obtain a back-extraction system;

[0008] The organic phase includes HBL121 and a diluent;

[0009] The stripping agent contains dissolved carbon dioxide.

[0010] The method according to embodiments of the present invention has at least the following beneficial effects:

[0011] (1) HBL121 is usually used to extract metal ions such as gallium. This invention creatively uses it to extract lithium in solution, achieving good extraction results. Compared with traditional extraction methods such as TBP, the effect is better.

[0012] (2) Typically, the stripping agent for lithium extraction is an aqueous solution of hydrochloric acid or sulfuric acid. Acidic conditions can cause severe corrosion to equipment, especially metal equipment, and simultaneously introduce impurity ions. This invention creatively uses an aqueous solution containing dissolved carbon dioxide for stripping, in which only a small amount of carbon dioxide is converted into carbonic acid (the remainder exists as carbon dioxide). Furthermore, a small amount of carbonic acid dissociates to produce HCO3. - or CO3 2- (K1 at 25℃ = 4.3 × 10⁻⁶) -7 K2 = 4.8 × 10 -11 ), and simultaneously contribute H + Therefore, the hydrogen ion concentration (acidity) in the stripping agent is lower, which can minimize corrosion to the instrument.

[0013] (3) If hydrochloric acid / sulfuric acid is used for back-extraction, lithium will be converted into lithium sulfate or lithium chloride during the concentration process of the back-extraction system. The solubility of these substances in water increases with increasing temperature.

[0014] This invention uses an aqueous solution of carbon dioxide for back-extraction, during which the following reaction occurs:

[0015] R HBL121 -Li + CO₂ + H₂O == LiHCO₃ + R HBL121 -H, where R HBL121 HBL121 represents the binding state;

[0016] During the heating and concentration process in the back-extraction system, lithium bicarbonate decomposes to produce lithium carbonate. Lithium carbonate has low solubility in water, and its solubility decreases with increasing temperature.

[0017] Therefore, the method provided by this invention can save the time and energy required for concentration of the back-extraction system, shorten the process flow and cost, and improve the lithium yield.

[0018] (4) The stripping agent used in this invention has a certain specificity for lithium ions, but has almost no stripping effect on magnesium, iron, calcium and other elements in the supported organic phase, thus improving the purity of the final lithium carbonate.

[0019] According to some embodiments of the present invention, the lithium-containing solution includes at least one of lithium ore leaching solution, enriched seawater, and lithium battery recovery solution.

[0020] According to some embodiments of the present invention, the lithium content in the lithium-containing solution is 0.5 to 50 g / L.

[0021] According to some embodiments of the present invention, the lithium content in the lithium-containing solution is 5 to 15 g / L. For example, it can be about 10 g / L.

[0022] According to some embodiments of the present invention, the lithium-containing solution includes Na. + and SO4 2- .

[0023] According to some embodiments of the present invention, the lithium-containing solution contains Na + The content is 50–150 g / L. For example, it can be 80–120 g / L. More specifically, it can be about 100 g / L.

[0024] According to some embodiments of the present invention, the lithium-containing solution further includes K + The lithium-containing solution contains K + The concentration is 0–10 g / L.

[0025] According to some embodiments of the present invention, the pH of the lithium-containing solution is 5 to 8. This facilitates operation in a near-neutral environment.

[0026] According to some embodiments of the present invention, the pH of the lithium-containing solution is 6 to 7.

[0027] According to some embodiments of the present invention, the volume ratio of HBL121 in the organic phase is 20-60%.

[0028] According to some embodiments of the present invention, the volume ratio of HBL121 in the organic phase is 25-30%.

[0029] According to some embodiments of the present invention, the volume ratio of HBL121 in the organic phase is 35-40%.

[0030] The viscosity of the organic phase increases with the increase of the volume ratio of HBL121. This viscosity will affect the uniformity of mixing between the organic phase and the lithium-containing solution to a certain extent, thereby affecting the extraction efficiency.

[0031] According to some embodiments of the present invention, the diluent includes at least one of hydrogenated kerosene and sulfonated kerosene.

[0032] According to some embodiments of the present invention, the organic phase further includes a modifier. HBL121 is a polar extractant, while the diluent is usually a non-polar solvent, which easily leads to poor extraction efficiency due to poor miscibility and the formation of a third phase. Adding a modifier can solve the above problems to some extent.

[0033] According to some embodiments of the present invention, the modifier comprises at least one of an alcohol compound and an ester compound. The modifier can increase the solubility of the extractant in a diluent.

[0034] Furthermore, both alcohols and esters affect the hydrate Li[H2O]4. + It has a strong adsorption effect, therefore, using an organic phase including the modifier can avoid the use of co-extractants, thereby reducing the pretreatment process of the lithium-containing solution. Since co-extractants, especially ferric chloride co-extractants, can be eliminated, the pH of the lithium-containing solution can fluctuate in the near-neutral to weakly alkaline range, avoiding the corrosive effect of acidic environments on the instrument.

[0035] Furthermore, since the modifier has a strong adsorption effect on the hydrate, it can also act as an extractant. Therefore, the organic phase provided by the present invention has a higher lithium extraction performance than the traditional TPB extractant.

[0036] According to some embodiments of the present invention, the alcohol compound includes at least one of nonanol and decol. By controlling the type of alcohol compound, its solubility in water can be controlled. Using these two alcohol compounds can maximize the compatibility between the extractant and the diluent, and minimize the solubility of the organic phase in the lithium-containing solution.

[0037] According to some embodiments of the present invention, the ester compound includes at least one selected from ethyl salicylate, propyl salicylate, n-butyl salicylate, pentyl salicylate, hexyl salicylate, heptyl salicylate, n-octyl salicylate, and isooctyl salicylate. Similarly, by controlling the type of ester compound, its solubility in water is controlled.

[0038] According to some embodiments of the present invention, the ester compound includes isooctyl salicylate.

[0039] According to some embodiments of the present invention, the volume percentage of the modifier in the organic phase is 1-8%. Within this range, its compatibility effect can be fully utilized, while avoiding binding between the modifier and HBL121, thereby avoiding the influence of the modifier on the extraction effect.

[0040] According to some embodiments of the present invention, the volume percentage of the modifier in the organic phase is 4-6%.

[0041] According to some embodiments of the present invention, the O / A ratio of the extraction is 0.1 to 10:1. Theoretically, a higher O / A ratio results in a lower concentration of lithium ions in the raffinate phase; however, it also increases the amount of organic phase used, increasing the economic burden; and it can also adversely affect the subsequent lithium concentration. Therefore, selecting the above range can balance economic benefits and lithium extraction rate.

[0042] According to some embodiments of the present invention, the extraction time is 1 to 30 minutes. This time is the time for the organic phase and the lithium-containing solution to be mixed by shaking, which promotes sufficient contact between the two phases.

[0043] According to some embodiments of the present invention, the extraction time is 5 to 15 minutes.

[0044] According to some embodiments of the present invention, the extraction further includes allowing the mixture to stand and separate after the above-mentioned shaking and mixing. The duration of the standing and separating is not limited, and is determined by visually confirming that the two phases are completely separated. Specific times may be, for example, 5–30 min, or 10–15 min.

[0045] According to some embodiments of the present invention, the number of extraction stages is 1 to 3. If the number of stages is greater than 1, for example, 2, then in the first extraction of a later batch, the loaded organic phase from the second extraction of the previous batch is used as the organic phase. Unless otherwise specified, the above extraction conditions are for single-stage extraction.

[0046] According to some embodiments of the present invention, after extraction, the concentration of lithium in the raffinate phase is <10 mg / L.

[0047] To further improve lithium recovery efficiency, the raffinate phase is concentrated and then subjected to secondary extraction.

[0048] According to some embodiments of the present invention, the volume ratio of the carbon dioxide to the stripping agent is 0.7 to 2.5:1.

[0049] According to some embodiments of the present invention, the volume ratio of the carbon dioxide to the stripping agent is 0.7 to 0.8:1.

[0050] According to some embodiments of the present invention, the pH of the back-extraction agent is 2 to 6. At 25°C and one atmosphere, the pH of a saturated aqueous solution of carbon dioxide is approximately 5.6. In practice, to obtain the desired pH, pressure treatment can be performed to increase the dissolved carbon dioxide content in the aqueous solution and simultaneously decrease its pH.

[0051] According to some embodiments of the present invention, the pH of the back-extraction agent is 5 to 6.

[0052] To reuse the organic phase, the back-extracted supported organic phase can be regenerated using a 6–8 mol / L hydrochloric acid aqueous solution. This regeneration involves shaking and mixing the hydrochloric acid aqueous solution and the back-extracted supported organic phase, followed by separation. The O / A ratio of the shaking mixture is 1:0.1–2. The shaking and mixing time is 5–30 min. This removes impurities from the back-extracted supported organic phase.

[0053] The concentration of the hydrochloric acid aqueous solution used for regeneration is 6.2–7 mol / L.

[0054] According to some embodiments of the present invention, the O / A value of the back-extraction is 1:0.1 to 4.

[0055] According to some embodiments of the present invention, the O / A value of the back-extraction is 1:0.2 to 0.8. Thus, when the volume of the back-extractant is less than the volume of the supported organic phase, the back-extraction also has the function of concentrating lithium.

[0056] According to some embodiments of the present invention, the back-extraction time is 5 to 60 minutes. This time is the duration of the shaking mixing.

[0057] According to some embodiments of the present invention, the back-extraction time is 10 to 20 minutes.

[0058] According to some embodiments of the present invention, the back-extraction further includes allowing the phases to separate after the above-mentioned shaking and mixing. The duration of the separation is not limited, and is determined by visually confirming that the two phases are completely separated. Specific time may be, for example, 5 to 30 minutes.

[0059] According to some embodiments of the present invention, the method further includes sequentially heating the back-extraction system and performing solid-liquid separation. The solubility of lithium carbonate in water decreases with increasing temperature, and heating can promote the decomposition of lithium bicarbonate into lithium carbonate. Therefore, the heating can improve the lithium recovery efficiency from the lithium-containing solution.

[0060] According to some embodiments of the present invention, the heating temperature is ≥60°C. The heating duration is not limited, but is determined by the precipitation and conversion of lithium bicarbonate into lithium carbonate. For example, it can be >30 minutes.

[0061] According to some embodiments of the present invention, the heating temperature is 80–100°C.

[0062] Within the above temperature range, the solubility of lithium carbonate decreases, and it will precipitate in solid form.

[0063] According to an embodiment of a second aspect of the present invention, the method is provided for use in the treatment of lithium ore leaching solutions, enriched seawater, or lithium battery recovery solutions.

[0064] Since the methods mentioned in other embodiments are used in all the applications described above, they possess all the technical effects of those methods. Specifically, they can significantly improve the lithium recovery rate from the solution, and the recovery system is simple, easy to operate, and has low corrosiveness to equipment.

[0065] According to an embodiment of a third aspect of the present invention, a system for carrying out the method is provided, the system comprising an extraction unit, a back-extraction unit, and a crystallization unit connected sequentially via pipes.

[0066] According to some embodiments of the present invention, the extraction unit includes an extraction tank, and an organic phase storage tank and a lithium-containing solution storage tank connected to the extraction tank.

[0067] According to some embodiments of the present invention, the back-extraction unit includes a back-extraction tank and a back-extraction agent storage tank connected to the back-extraction tank.

[0068] According to some embodiments of the present invention, the stripping agent storage tank is provided with a gas inlet.

[0069] According to some embodiments of the present invention, the stripping agent storage tank is a sealed pressure-bearing structure. This allows carbon dioxide to be pressurized and introduced, increasing the carbon dioxide content in the stripping agent.

[0070] According to an embodiment of the fourth aspect of the present invention, the method is provided for use in the preparation of lithium carbonate for lithium-ion batteries.

[0071] Since the method can produce lithium carbonate with high purity, it is expected to be widely used in the acquisition of raw materials for lithium-ion battery preparation.

[0072] Unless otherwise specified, the term "about" in this invention actually means that the error is allowed to be within ±2%, for example, about 100 is actually 100 ± 2% × 100.

[0073] Unless otherwise specified, "between" in this invention includes the number itself, for example, "between 2 and 3" includes the endpoint values ​​2 and 3.

[0074] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0075] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0076] Figure 1 This is a flowchart illustrating an embodiment of the present invention.

[0077] Figure 2This is a schematic diagram of the system used in the embodiments of the present invention.

[0078] Figure label:

[0079] Extraction unit 100, organic phase storage tank 110, lithium-containing solution storage tank 120, extraction tank 130;

[0080] Back-extraction unit 200, back-extraction agent storage tank 210, gas inlet 211, back-extraction tank 220;

[0081] Crystallization unit 300;

[0082] Pipeline 400. Detailed Implementation

[0083] The following will describe the concept and technical effects of the present invention clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0084] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0085] Example 1

[0086] refer to Figure 1 The process shown in this embodiment illustrates a method for recovering lithium from a lithium-containing solution. The specific steps are as follows:

[0087] S1. Extraction of the lithium-containing solution with an organic phase yields a supported organic phase and a raffinate phase; wherein...

[0088] The organic phase is a mixture of HBL121 (a special extractant developed by Central South University and produced by Hunan Hongbang Materials Technology Co., Ltd.), sulfonated kerosene (diluent), and decanol (modifier) ​​in a volume ratio of 40:55:5.

[0089] The lithium-containing solution is a lithium-containing sodium sulfate solution obtained after leaching and impurity removal from lithium ore. Its composition is Na = 100 g / L; Li = 10 g / L, and pH is 10-12. After pH adjustment, the pH is approximately 7.

[0090] The O / A ratio for single-stage extraction was 0.5:1; the extraction time was 10 min, and the subsequent separation time was approximately 10 min.

[0091] In this example, the extraction stage is 2.

[0092] S2. The supported organic phase is back-extracted using a back-extracting agent to obtain a back-extraction system; wherein...

[0093] The back-extraction agent is an aqueous solution containing dissolved carbon dioxide. The concentration of carbon dioxide in the extractant is approximately 750 mL / L, and the pH is approximately 5.5.

[0094] The O / A ratio for back-extraction was 0.8:1, and the time was 10 minutes. The subsequent separation time was approximately 8 minutes.

[0095] S3. Heat the back-extraction system obtained in step S2 until lithium carbonate is precipitated.

[0096] The heating temperature is 80℃ and the duration is 5 hours.

[0097] S4. Perform solid-liquid separation on the mixture obtained in step S3, and dry the resulting solid product to obtain the final product.

[0098] refer to Figure 2 The system used in this embodiment includes an extraction unit 100, a back-extraction unit 200 and a crystallization unit 300 connected in sequence via a pipe 400.

[0099] The extraction unit includes an extraction tank 130, an organic phase storage tank 110 and a lithium-containing solution storage tank 120 connected to the extraction tank 130; the back-extraction unit includes a back-extraction tank 220 and a back-extraction agent storage tank 210 connected to the back-extraction tank 220. The back-extraction agent storage tank 210 is provided with a gas inlet 211, through which carbon dioxide gas can be introduced. The back-extraction agent storage tank 210 is a sealed pressure-bearing structure, through which carbon dioxide can be introduced under pressure to increase the carbon dioxide content in the back-extraction agent.

[0100] Example 2

[0101] This embodiment implements a method for recovering lithium from a lithium-containing solution. The specific steps differ from those in Embodiment 1 in that:

[0102] In step S1, the modifier in the organic phase is isooctyl salicylate.

[0103] Example 3

[0104] This embodiment implements a method for recovering lithium from a lithium-containing solution. The specific steps differ from those in Embodiment 1 in that:

[0105] In step S1, the volume percentage of HBL121 in the organic phase is 25%, with the remainder made up by sulfonated kerosene. The time required for separation after extraction is approximately 5 minutes.

[0106] Example 4

[0107] This embodiment implements a method for recovering lithium from a lithium-containing solution. The specific steps differ from those in Embodiment 1 in that:

[0108] The O / A ratio of the back-extraction is approximately 0.2:1.

[0109] Example 5

[0110] This embodiment implements a method for recovering lithium from a lithium-containing solution. The specific steps differ from those in Embodiment 1 in that:

[0111] In step S1, the organic phase used is the reproduct of the loaded organic phase after back-extraction in Example 1.

[0112] The regeneration process involves mixing a 6.5M hydrochloric acid aqueous solution with the back-extracted supported organic phase by shaking for 15 minutes at an O / A ratio of 0.5:1, followed by separation.

[0113] Example 6

[0114] This embodiment implements a method for recovering lithium from a lithium-containing solution. The specific steps differ from those in Embodiment 1 in that:

[0115] In step S1, the organic phase used does not include the modifier, and the volume occupied by the original modifier is made up by the diluent.

[0116] Comparative Example 1

[0117] This comparative example demonstrates a method for recovering lithium from a lithium-containing solution. The specific steps differ from those in Example 1 in that:

[0118] In step S1, the extractant is replaced with TBP.

[0119] Comparative Example 2

[0120] This comparative example demonstrates a method for recovering lithium from a lithium-containing solution. The specific steps differ from those in Example 1 in that:

[0121] In step S2, the stripping agent is a 200 g / L aqueous solution of sulfuric acid.

[0122] In step S3, the mixture is heated until crystals precipitate, cooled to room temperature, and then filtered.

[0123] Test case

[0124] This example tested the composition of the products obtained in each step of the examples and comparative examples. Specifically, the concentration of each element was tested using ICP-OES, and the yield, purity, and other results were calculated accordingly. The specific results are shown in Table 1.

[0125] Table 1 Results of each step in Examples 1-6 and Comparative Examples 1-2

[0126] Extraction residue Li ppm Total extraction rate % Back-extraction rate % Lithium recovery rate % Example 1 7 99.93 96.6 96.5 Example 2 2 99.98 99.5 99.5 Example 3 16 99.84 96.3 96.1 Example 4 7 99.95 97.8 97.7 Example 5 23 99.77 96.0 95.8 Example 6 42 99.58 97.1 96.7 Comparative Example 1 65 99.35 96.2 95.6 Comparative Example 2 7 99.95 97.3 97.2

[0127] In Table 1, the lithium recovery rate is the ratio of the amount of lithium in the back-extraction system to the amount of lithium in the lithium-containing solution.

[0128] Comparing Examples 1 and 2, it can be seen that the performance of ester modifiers is slightly better than that of alcohol modifiers during the extraction process. This may be because the ester groups in ester modifiers have a stronger adsorption effect on lithium hydrates, thus also acting as an extractant. In other words, compared with Example 1, it is equivalent to increasing the concentration of extractant in the organic phase, thereby improving the single-stage extraction efficiency to a certain extent.

[0129] Comparing Examples 1 and 3, it can be seen that reducing the concentration of the extractant in the organic phase will reduce the extraction efficiency to some extent, but the reduction is very small. This may be because although the extractant concentration decreases, the viscosity of the organic phase also decreases, thereby increasing the uniformity of contact between the organic phase and the lithium-containing solution. Furthermore, when the viscosity of the organic phase decreases, the time required for separation is also significantly reduced.

[0130] Comparing Examples 1 and 4, it can be seen that within the range provided by the present invention, the back-extraction efficiency decreases slightly with the decrease of O / A value, but the decrease is very small. This indicates that the back-extraction agent provided by the present invention has good performance and can significantly concentrate lithium in aqueous solution during the extraction-back-extraction process.

[0131] Comparing Examples 1 and 5, it can be seen that the regenerated organic phase can also achieve lithium extraction. Its single-stage extraction efficiency is slightly lower than that of Example 1, but still superior to extractants such as TBP used in traditional techniques. Experiments show that the organic phase can be regenerated and reused approximately 10 times.

[0132] Comparing Examples 1 and 6, it can be seen that the organic phase of the default modifier can still achieve lithium extraction, but its single-stage extraction efficiency is slightly lower than that of Example 1. This is because HBL121 has insufficient solubility in the diluent and is prone to self-composite, thus affecting the lithium extraction effect.

[0133] Comparing Examples 1-6 with Comparative Example 1, it can be seen that HBL121 is slightly more effective than TBP, commonly used in conventional techniques, for lithium extraction. Furthermore, compared to the TBP system, the system provided by this invention can even eliminate the need for co-extraction and is less prone to the formation of a third phase. Moreover, the combination of HBL121 and the back-extraction agent used in this invention not only improves the back-extraction efficiency but also reduces the concentration of impurity ions in the back-extraction system and the resulting lithium carbonate. Therefore, in the method provided by this invention, a synergistic effect occurs between the organic phase and the back-extraction agent, significantly simplifying the composition of the extraction system, improving extraction and back-extraction effects, reducing extraction costs, and improving the quality of the product salt.

[0134] Comparing Examples 1-6 with Comparative Example 2, it can be seen that if a conventional sulfuric acid aqueous solution is used as the stripping agent, a lithium stripping effect comparable to that of the examples can be obtained. However, the lithium in the resulting stripping system is lithium sulfate, whose solubility increases with increasing temperature, and its solubility is higher than that of lithium carbonate in Examples 1-6 (the solubility of lithium carbonate is shown in Table 2). Therefore, the crystallization recovery rate of the obtained lithium salt decreases, and thus the overall lithium recovery rate also decreases.

[0135] Table 2. Solubility of lithium carbonate in water at different temperatures

[0136] substance 0℃ 10℃ 20℃ 30℃ 40℃ 50℃ 60℃ 70℃ 80℃ 90℃ 100℃ <![CDATA[Li2CO3]]> 1.54 1.43 1.33 1.26 1.17 1.08 1.01 / 0.85 / 0.72

[0137] Furthermore, this example also tested the crystallization recovery rate of lithium carbonate (lithium in the recovered solid lithium carbonate / lithium in the back-extraction system) and the purity of the obtained lithium carbonate in steps S3-S4. The results showed that, due to the specificity of the extraction process for Li and the absence of introduced impurities, the purity of the obtained lithium carbonate was ≥99.9%. Further, in Examples and Comparative Example 1, the crystallization recovery rate was ≥99.5%. In Comparative Example 2, the crystallization recovery rate was approximately 96%. In other words, this invention significantly improves the overall lithium recovery rate and reduces equipment corrosion during the extraction process by controlling the reagents used in the extraction and back-extraction processes.

[0138] In summary, the method provided by this invention significantly improves extraction and back-extraction efficiency, enhances the overall lithium recovery efficiency, and increases the purity of the obtained lithium salt by adjusting the composition of the organic phase and the back-extraction agent. Simultaneously, it reduces the compositional complexity of the entire extraction system, improving safety and economic efficiency. Furthermore, due to the high purity of the obtained lithium carbonate, the method provided by this invention is expected to find wide application in the preparation of lithium-ion battery materials.

[0139] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for recovering lithium from a lithium-containing solution, characterized by, The method comprises extracting the lithium-containing solution with an organic phase to obtain a loaded organic phase, and stripping the loaded organic phase with a stripping agent to obtain a stripping system; The organic phase comprises HBL121, a diluent and a modifier; the modifier comprises at least one of an alcohol compound and an ester compound; The pH of the lithium-containing solution is 5-8; The stripping agent is an aqueous solution dissolving carbon dioxide.

2. The method of claim 1, wherein, In the organic phase, the volume ratio of the HBL121 is 20-60%.

3. The method of claim 1, wherein, The diluent comprises at least one of hydrogenated kerosene and sulfonated kerosene.

4. The method of claim 1, wherein, The volume percentage of the modifier in the organic phase is 1-8%.

5. The method of claim 1, wherein, The O / A value of the extraction is 0.1-10:

1.

6. The method of claim 1, wherein, The volume ratio of the carbon dioxide to the stripping agent is 0.7-2.5:

1.

7. The method of claim 1, wherein, The pH of the stripping agent is 2-6.

8. The method of claim 1, wherein, The O / A value of the stripping is 1:0.1-4.

9. The method according to any one of claims 1 to 8, characterized in that, The method further comprises sequentially heating the stripping system and solid-liquid separation.

10. Use of the method according to any one of claims 1-9 in the treatment of lithium ore leaching solution, enriched seawater or lithium battery recovery solution.

11. A system for carrying out the method according to any one of claims 1 to 9, characterized in that The system comprises an extraction unit, a stripping unit and a crystallization unit connected in sequence via pipelines.

12. Use of the method according to any one of claims 1-9 in the preparation of lithium carbonate for lithium ion batteries.

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